The new diploid grapevine variety of the present invention was created during the course of a grapevine breeding program that was carried out in Australia wherein two parents were crossed which previously had been studied in the hope that they would contribute the desired characteristics. The female parent (i.e., seed parent) was the complex hybrid Vitis spp. ‘39-639 Seyve-Villard’ variety (non-patented in the United States). Such female parent is listed in Galet, P., “Cépages et vignobles de France, Tome I Les Vignes Américaines” (1988) as being an early-maturing, disease resistant white-berried interspecific hybrid of unknown origin. The female parent was chosen as a seed parent primarily in view of its resistance to mildew diseases, such as downy mildew and powdery mildew. The male parent (i.e., pollen parent) was the ‘Beauty Seedless’ variety (non-patented in the United States). The ‘Beauty Seedless’ variety is recognized for its ability to produce with high productivity bunches of early-ripening stenospermocarpic egg-shaped berries having a distinctive light spicy flavor. The parentage of the new variety of the present invention can be summarized as follows:‘39-639 Seyve-Villard’ Vitis spp. Complex Hybrid×‘Beauty Seedless’ Vitis vinifera.
The controlled cross that resulted in the production of the new variety of the present invention was carried out during Spring 1980 (Southern Hemisphere). Flowers of the female parent were emasculated and were thereafter protected from unintended cross-pollination by enclosure in pollen-proof bags. Approximately twenty-four hours following emasculation, pollen from the male parent was applied to the receptive stigma of the female parent. Such pollen had been collected from unopened flowers of male parent, and thereafter was dried in Petri dishes at 40° C. under conditions where contamination by other Vitis pollen was precluded. The resulting seeds from the cross were extracted from the fruits in Autumn 1981 (Southern Hemisphere) and were sown in a greenhouse while employing standard seed bed conditions. Emergent seedlings were transferred to standard potting mix and were maintained in pots under greenhouse conditions until they were planted in a vineyard during Spring 1981 (Southern Hemisphere). Thereafter, the plants were grown and evaluated while using standard grapevine cultivation conditions.
A single plant of the new variety was selected during 1988 from among the resulting siblings. The new variety was found to possess a combination of characteristics unlike that of its siblings and unlike that of either of the respective parent plants. The resulting plant has been carefully observed, tested and evaluated in replicated plantings and trials while growing on its own roots or when top-worked onto a range of grape rootstocks including Vitis champinii ‘Ramsey’ (non-patented in the United States).
It was found that the new grapevine of the present invention displays the following combination of characteristics:                (a) displays high stenospermocarpic fruit production,        (b) forms early-ripening juicy relatively large bunches of small substantially spherical berries that develop an intense black-purple coloration upon maturity,        (c) displays superior resistance to downy mildew and powdery mildew, and        (d) is particularly well suited for the production of dried currants.        
Vines of the new variety have been found to be very fruitful with cane pruning systems being recommended for trellis drying.
The new variety well meets the needs of the horticultural industry. It can be grown to advantage for the production of dried vine fruit. It also may be used for the production of table grapes or used for making wine or grape juice.
The dried berries of the new variety have been shown to advantageously possess high levels of antioxidants. The ‘Zante’ and ‘Carina’ varieties (both non-patented in the United States) have previously commonly been used for the production of dried currants in Australia. When the hydrophilic oxyradical scavenging capacity of the fruit of these varieties was compared with that of the new variety, this capacity for the new variety was found to be approximately three times that of the ‘Zante’ variety and approximately 30 percent higher than that of the ‘Carina’ variety.
Vines of the new variety have displayed superior resistance to downy mildew (Plasmopara vitriola) and powdery mildew (Uncinula necator) when compared to other commonly grown grape varieties. For instance, when the new variety was compared at Merbin, NW Victoria, Australia, to the ‘Sultana’ variety (non-patented in the United States) under conditions conducive to disease infestations while using IPGRI Descriptors for Grapevine (1997), the comparative field ratings were obtained as follows:
‘Sultana’Present VarietyDowny Mildew4.6 to 5.81.8 to 2.2Powdery Mildew6.6 to 7.03.8 to 4.2The reported values are without units and are in accordance with the standard IPGRI Disease Rating Scale. Lower ratings are recognized to be indicative of increased resistance of the vine to disease infection and are not a percentage of infected plants. Field ratings similar to those of ‘Sultana’ have been observed for the ‘Beauty Seedless’ variety.
The new variety of the present invention does not require the use of a setting spray as other grape varieties commonly used to produce dried currants, such as the ‘Zante’ variety. Also, the new variety can be grown with reduced agrichemical usage making it well suited for organic grape production.
The new variety can be grown on its own roots or when grafted on standard rootstocks, such as ‘Ramsey’, ‘Paulsen’, ‘Schwarzmann’, and ‘140R’ (each non-patented in the United States). When grown in northwest Victoria, Australia on ‘Ramsey’ rootstock, it is estimated that the vigor is increased by approximately 50 percent with a commensurate increase in yield.
The new variety of the present invention can be readily distinguished from its parental varieties upon an inspection of the fruit. More specifically, the grapes of the ‘39-639 Sayve-Villard’ variety are larger, possess seeds, are unsuitable for drying to produce currants, and are borne in smaller bunches. The ‘Beauty Seedless’ variety forms larger black berries that are unsuitable for drying to produce currants, and is considerably more susceptible to downy mildew and powdery mildew.
The new variety of the present invention has been found to undergo asexual propagation at Irymple and Cardross, NW Victoria, Australia, by a number of routes including budding, top-working, and the rooting of cuttings. Accordingly, the new variety has been found to undergo asexual propagation in a true-to-type manner. During such propagation, the new variety has been found to be compatible with a wide range of rootstocks. Grafting has been found to make possible optimum vigor and canopy cover.
The new variety initially was named ‘M 48-42’, and sometimes has been identified as ‘Black Gem’.